The formulation of conditioning shampoos has been difficult because of several reasons. One problem is that anionic surfactants, which are desired for their excellent cleaning ability, are incompatible with cationic surfactants, which are desired for their hair conditioning properties.
Another problem is that water-insoluble conditioning agents, such as silicone-containing compounds, which are added to provide a degree of softness and luster to the hair typically cause the composition to be unstable. A related problem is that it is difficult to keep these silicone-containing compounds suspended or maintained in a stable form while retaining the performance attributes desired from the conditioning shampoo. One solution to that problem has been proposed in U.S. Pat. No. 5,198,209 where a particular N-alkylated pyrolidone is suggested to be useful for maintaining the composition in a stable form. Unfortunately, the particular pyrolidone is not a suspending agent and it is has now been found that after a few days at elevated temperatures on the order of 40.degree. C. to about 50.degree. C., a white, creamy layer forms at the surface.
Another solution to that problem that has been proposed by Bergmann, U.S. Pat. Nos. 5,275,761, 5,358,667, and 5,456,863 is to use a polyhydric compound as an essential element to emulsify, add phase-stability, prevent anionic-cationic interaction and couple the insoluble conditioning agent with the cationic surfactant. The polyhydric is used with a carboxylated surfactant, a hydrophilic quaternary ammonium, or a fafty alkyl compound.
Surprisingly and unexpectedly, it has been found that a conditioning shampoo can be prepared that is substantially free of a polyhydric compound. In fact, when a polyhydric compound is added to the conditioning shampoo of the present invention the viscosity and foam volume were significantly reduced, with no increase in stability to off-set the negative impact on viscosity and foam volume.